Apparatus for recovering solvents.



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APPARATUS FOR RECOVERING SOLVENTS.

APPLICATION FILED ocT. I6. 1912.

Patented Aug. 14, 1917.

2 SHEETS-SHEET I.

F. KNIFFEN.

APPARATUS FOR RECOVERING SOLVENTS.

APPLlcATioN FILED ocT.16.1912.

ly236,'719 PatentedAug. 14,191.7.

Zl/ o o y /WM GWMWAM UNITED STATES PATENT OFFICE.

:FREDERICK KIN'IFFEN, 0F WILMINGTON, DELAWARE, ASSIGNOR TO E. I. \DUPONT by NEMOURS POWDER COMPANY, OF WII.1V.[IN'G'1ON 1 DELAWARE, ACORPORATION OF NEW JERSEY.

To all whom t may concer/n.'

Be it lmown that I, FREDERICK KNHFEN, of Wilmington, in the county ofNew Castle and in the State of Delaware, have invented a certain new anduseful Improvement in Apparatus for Recovering Solvents, and do herebydeclare that the following is a full, clear, and exact descriptionthereof.

My invention relates particularly to a method and means for recoveringsolvents used in coating compositions, although it may be adapted to usein any other connection where it is desired to recover solvents. Myinvention is particularly applicable to the recovery of solvents fromcoatings of paper or textile fabrics containing india rubber, pyroxylin,oils, paints or varnishes,

and employing volatile solvents such as benzol, alcohol, ether, acetoneor turpentine.

The object of my invention 1s to render the recovery of solvents morecomplete than has hitherto been possible; to render 'the danger ofexplosion as slight as possible, and to improve the quality of theproduct as well as the convenience and economy of operating theapparatus used for recovering the solvent.-

My invention is carriedout by passing the goods in a continuous coatedweb through an evaporating chamber where it is submitted to the actionof a heated current of air. The air in the evaporating chamber havingtaken up the solvent evaporated is conducted to a condenser, where aportion of 'the solvent is condensed, the air with the residual solventbeing again heated and returned to the evaporating chamber, while thecondensed solvent, after purification, is employed in preparing freshcoating compositions. In carrying out my invention, I also make use ofan apparatus which has a very small internal capacity so that a smalleramount of solvent is required to charge the free space in the interiorthereof, and the condensation of the solvent takes place earlier, andthere is smaller loss in case it is necessary 'to Open the same. Afurther advantage of the small capacity is that in the case of anexplosion very little damage will result. Still a further advantage isthat in case of temperature changes in the interior of the apparatusthere will be a very small amount of air or vapor either sucked in ordischarged from the apparatus. v

My apparatus is so arranged that in case Specication of Letters Patent.

APPARATUS FOB BECOVEING SOLVENTS.

vPatented Aug. 14, 1917.

Application led October 16, 1912. Serial No. 726,015.

of an explosion the pressure will be relieved by elevatingr a coverwhich is loosely supported on the top of the apparatus, thereby avoidingvery great damage in case of an explosion. The presence of a cover ofthis kind also enables the heating devices on the interior, which arelocated above the surface of the coated web, to be more readilyaccessible when it is found desirable to reach the accumulations ofthis, character could take lace, there might be considerable danger ofe, possibly resulting inan explosion, considering the nature of thematerials from which coatings are ordinarily made. A further distinctadvantage of the arrangement of the heating apparatus above the coatedsurface is that a less depth for the entire apparatus is required, andwhen used in connection with the automatic draft which is the basis ofthe circulation of the air, 'there is little risk of overheating theweb.

While my process is capable of being carried out in many different typesof apparatus, I have shown only certain modiiications of apparatus whichI may use, in the accompanying drawings, in which- Figure 1 is avertical transverse section of one form of apparatus in which my processmay be carried out, the parts being shown somewhat diagrammatically;

Fig. 2 is a similar view of another type of apparatus which I may use;

Fig. 3 is a similar view of still another type of apparatus;

Fig. 4 is a similar view of another type of apparatus used for the samepurpose; and,

Fig. 5 is also a similar view of another type of apparatus used for thesame purpose.

In the drawings, reference being had to Fig. 1, a traveling web-1 ofpaper or textile fabric, after being coated, is conveyed through anevaporating chamber 2 by any suitable means. While in the evaporatingchamber 2, the web l passes beneath a series of heating coils 3 forevaporating the volatile liquids from the coating composition. Theevaporating chamber is covered by an easily-removable cover 4, the edgesof which are rendered air-tight by being retained in a liquid seal 5,filled with castor oil or other liquid, or in any other conven- ,ientmanner as by fastening with adhesive tape. The current of air which iscirculating through said chamber is led therefrom downwardly through avertical passage 6 containing, at the upper end thereof, a series ofcooling coils 7 to increase the specific gravity of the solvent-ladenair, and to cool the same preliminary to the condensation and separationof the solvent therefrom. The cooled current of air carrying the solventvapors is then conducted through a horizontally disposed condenser 8over a series of cooling coils 9. The series of coils 9 is fed with acurrent of cold water or other refrigerating agent through an inlet 10and discharges the same through an outlet 11. At the bottom of thecondenser 8 there is a discharge pipe 12 for the condensed solvent. Theair having had part of its contained solvent removed by condensation isreheated in any convenient manner as by passing over steam coils 14. Thedensity being thereby reduced, it rises through a vertical passageway 13and then returns to the evaporating chamber for re-use as before. Abaffle 15 is provided to keep scrapings of coating material from fallingdown the flue 13 and to better direct the circulation of the air.

The type of apparatus shown in Fig. 2 is constructed in the same manneras that shown in Fig. 1, except that an elevated side chimney isemployed to assist the draft, thus enabling the other parts to be builtmore compactly without sacrificing the efficiency of circulation,attained in the form shown in Fig. 1. In the form shown in Fig. 2, thisdifference in construction requires the solvent-laden air to be ledupwardly over a baille plate 16 to an upwardly directed chamber 17 overa baffle plate 18, and downwardly through the vertical passageway 6,over the cooling coils 7. The long passageway 6 materially assists ingiving the circulating current of air the required speed.

The form of apparatus shown in Fig. 3 is the same as that shown in Fig.1, except as follows: After leaving the evaporating chamber 2, thesolvent-laden air is conducted directly into a horizontal iue 19 locatedimmediately below the evaporating chamber and from this point it is leddirectly to the vertically disposed condenser 20'having a set of coolingcoils 21. The air which has been freed from the surplus solvent isthereafter led into contact with the reheating coils 14 located in thevertical passageway 13. This arrangement avoids the loss of any space inthe middle of the apparatus between the several chambers.

Another and more compact form of apparatus is shown in Fig. 4 in whichthe construction is the same as in the case of the modification shown inFig. 1, except that the condenser 8 is located immediately below theevaporating chamber 2, the vertical passageways 6 and 13 being made muchwider to compensate for their shortness, and bafiie plates 22 and 23being located at the inlet and outlet ends of the condenser at the topthereof, and a baiiie plate 24 being located at the bottom of thecondenser at the outlet thereof to keepthe condensed solvent away fromthe reheating arrangement.

In Fig. 5 I have shown a type of apparatus which is the same as thatshown in Fig. 4, except that a passageway 17 and a passageway 6,together with baffle plates 16 and 18 are utilized similar to thoseshown in the form in Fig. 2. This type of apparatus gives a somewhatbetter circulation than that shown in Fig. 4, owing to the added lengthof the passageway 6.

The forms shown in Figs. 4 and 5 have the advantage that the condensedsolvent is delivered at a high level, and that the space below theapparatus is entirely unencumbered.

The operation of my process is substantially the same in all of thedifferent forms of apparatus, and is as follows: The coated web beingconstantly moved through the apparatus, the body of air containedtherein is iirst heated by the reheating coils, thereby decreasing itsdensity, and increasing its evaporating capacity. The heated current ofair is then conducted over the vcoated surface which is at the same timesubjected to the heat radiated from the heating coils located above thesame. The heat lost by the coated web and the air in contact with it,due to the latent heat of evaporation is made good by radiation from thecoil above in the upper part of the evaporating chamvber, thus enablinga smaller volume of circulated air to effect the same amount ofevaporation and a higher concentration of evaporated solvent to bereached, as well as more uniform and rapid drying, without risk ofoverheating. The current of air carrying a large percentage ofevaporated solvent, is now cooled to the saturation point by contactwith the cooling coils 7. The mixed air and solvent vapors thereuponacquire their greatest density, and fall at considerable speeddownwardly through the vertical passageway 6 until the condenser isreached. The available part of the solvent is then condensed upon thesurface of the cooling coils in the condenser, and is separated out andremoved through the discharge pipe 12 located at the bottom thereof. Aportion of the solvent having now been separated from the current ofair, the latter is again conducted upwardly intorcontact with theheating coils 14, thereby decreasing the specific gravity of the sameand causing it to again circulate in contact with the coating to bedried. a

While I have shown and described abov only certain forms of the processand apparatus which may e used for the carrying out of my invention, Iwish it to be understood that many changes may be made' condenserlocated below the evaporating chamber, and means for circulating acurrent of a gasthrough the same by convection, comprising a preliminarycooler loycated at the outlet from the. evaporating chamber, andapreliminary heater located in advance of the evaporating chamber.

2. In a device of the character described, a shallow evaporatingchamber, means for' supporting a web to be dried therein, and means forcirculating a current1 of gas therethrough by convection, comprising adownwardly directed cooling chamber at one end of the evaporatingchamber, an upwardly directed supply passage at the other end of theevaporating chamber, and a condensing chamber connecting the lower endsof the cooling chamber and supply passage.

3. In a device of the character described, a shallow evaporatingchamber, means for supporting a web to be dried therein, and means forcirculating a -current of gas therethrough by convection, comprising adownwardly directed cooling chamber at one end of the evaporatingchamber, an upwardly directed preheating supply passage at the other endof the evaporating chamber, and a condensing chamber connecting thelower ends of the cooling chamber and preheating supply passage.

In testimony that I claim the foregoing I have hereunto set my hand.

FREDERICK KNIEEEN. Witnesses: l

JOHN E. Emmons, P., E. STRICKMND.

